A gallium nitride (GaN)-based compound semiconductor is a direct transition type semiconductor and can control a wavelength from visible rays to ultraviolet rays. The gallium nitride-based compound semiconductor has high thermal and chemical stability and high electron mobility and saturated electron velocity. The gallium nitride-based compound semiconductor has excellent physical properties such as a large energy band gap as compared to known gallium arsenic (GaAs) and indium phosphorus (InP)-based compound semiconductors. On the basis of these properties, an application range of the gallium nitride-based compound semiconductor has been expanded to optical devices such as light emitting diodes (LEDs) of a visible ray region and laser diodes (LDs), and the next-generation wireless communication and satellite communication systems requiring high power and high frequency properties, which are fields having a limitation when using known compound semiconductors.
Performance of a gallium nitride-based electronic device is determined by an epitaxial structure, a process technology such as ohmic contact by a low resistance metal material and Schottky contact having high bather potential and a device design for determining a range of high frequency operation and current operation. Here, the epitaxial structure includes a barrier layer constituted by aluminum gallium nitride (AlGaN), indium aluminum nitride (InAlN), aluminum nitride (AlN) and the like, a channel layer used as an electron movement path and a semi-insulating layer for device isolation and reduction in leakage current.
However, when implementing integrated structures having various properties on a single substrate at the same time, there are many limitations in designing of the epitaxial structure, a device process and designing of a device, which is an obstacle to implementing a GaN-based electronic device.
Accordingly, in order to manufacture a GaN-based field effect transistor (FET), it is necessary to develop an epitaxial structure, a process technology and a device design technology that can manufacture various FET devices on a single substrate.